Messages in this thread Patch in this message | | | Subject | [PATCH] iommu/amd: Only unmap large pages from the first pte | From | Alex Williamson <> | Date | Fri, 21 Jun 2013 14:33:19 -0600 |
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If we use a large mapping, the expectation is that only unmaps from the first pte in the superpage are supported. Unmaps from offsets into the superpage should fail (ie. return zero sized unmap). In the current code, unmapping from an offset clears the size of the full mapping starting from an offset. For instance, if we map a 16k physically contiguous range at IOVA 0x0 with a large page, then attempt to unmap 4k at offset 12k, 4 ptes are cleared (12k - 28k) and the unmap returns 16k unmapped. This potentially incorrectly clears valid mappings and confuses drivers like VFIO that use the unmap size to release pinned pages.
Fix by refusing to unmap from offsets into the page.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Cc: stable@vger.kernel.org --- drivers/iommu/amd_iommu.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index 21d02b0..a3c3389 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -1484,6 +1484,10 @@ static unsigned long iommu_unmap_page(struct protection_domain *dom, /* Large PTE found which maps this address */ unmap_size = PTE_PAGE_SIZE(*pte); + + /* Only unmap from the first pte in the page */ + if ((unmap_size - 1) & bus_addr) + break; count = PAGE_SIZE_PTE_COUNT(unmap_size); for (i = 0; i < count; i++) pte[i] = 0ULL; @@ -1493,7 +1497,7 @@ static unsigned long iommu_unmap_page(struct protection_domain *dom, unmapped += unmap_size; } - BUG_ON(!is_power_of_2(unmapped)); + BUG_ON(unmapped && !is_power_of_2(unmapped)); return unmapped; }
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